Is the plateau state in GRS 1915+105 equivalent to canonical hard states?

TL;DR

This study investigates whether the unique plateau state of GRS 1915+105 is equivalent to the typical hard state in black hole X-ray binaries by analyzing multi-wavelength data with a steady-state outflow model.

Contribution

The paper applies a steady-state outflow model to multi-wavelength observations of GRS 1915+105's plateau state, revealing differences from the canonical hard state.

Findings

Significant differences between two plateau states.

Differences between plateau states and canonical hard state parameters.

Implications for GRS 1915+105's relationship to typical black hole states.

Abstract

GRS1915+105 is a very peculiar black hole binary that exhibits accretion-related states that are not observed in any other stellar-mass black hole system. One of these states, however -- referred to as the plateau state -- may be related to the canonical hard state of black hole X-ray binaries. Both the plateau and hard state are associated with steady, relatively lower X-ray emission and flat/inverted radio emission, that is sometimes resolved into compact, self-absorbed jets. However, while generally black hole binaries quench their jets when the luminosity becomes too high, GRS1915+105 seems to sustain them despite the fact that it accretes at near- or super-Eddington rates. In order to investigate the relationship between the plateau and the hard state, we fit two multi-wavelength observations using a steady-state outflow-dominated model, developed for hard state black hole binaries. The data sets consist of quasi-simultaneous observations in radio, near-infrared and X-ray bands. Interestingly, we find both significant differences between the two plateau states, as well as between the best-fit model parameters and those representative of the hard state. We discuss our interpretation of these results, and the possible implications for GRS 1915+105's relationship to canonical black hole candidates.